An image generation device in the related art adopts a technique to output an image of a string made up of characters to an output device, such as a display (Patent Literature 1). Such an image generation device rasterizes an outline font or the like represented as curves defined by functions, such as a Bezier curve and a spline curve, according to a size of each letter to be displayed by using a font rasterizer, and outputs an image of letters of a shape that best suits an output region.